DEVELOPING CANCERIN THIS SECTION YOU WILL LEARN:• CHANGES IN THE GENETIC MATERIAL IN ANORMAL CELL UNDERPIN CANCER INITIATIONAND DEVELOPMENT IN MOST CASES.• A CANCER CELL’S SURROUNDINGS INFLUENCETHE DEVELOPMENT AND PROGRESSION OFDISEASE.• THE MOST ADVANCED STAGE OF CANCER,METASTATIC DISEASE, ACCOUNTS FOR MORETHAN 90 PERCENT OF CANCER DEATHS.• THE MORE WE KNOW ABOUT THE BIOLOGYOF CANCER, THE MORE PRECISELY WE CANPREVENT, DETECT, DIAGNOSE, AND TREAT IT.

Cancer arises when the orderly processes that control the
multiplication and life span of normal cells go awry. As a
result, the cells start multiplying uncontrollably, fail to die
when they should, and accumulate, either forming a tumor
mass in any organ or tissue of the body or crowding out
the normal cells in the blood or bone marrow. Over time,
tumors can enlarge as more cells accumulate, until some
cells gain the ability to invade local tissues and spread, or
metastasize, to distant sites (see Figure 3). ;e emergence
of metastatic cancer is a dire occurrence that accounts for
more than 90 percent of cancer deaths.

;e changes in cell behavior that occur during the
initiation, development, and progression of a cancer are
predominantly a result of changes in the genetic material
of the cells. ;e length of time it takes for a cancer to
develop varies widely and depends on the identity, order,
and speed at which changes in the genetic material
accumulate. Numerous interrelated factors, such as a
person’s genetic makeup and environmental factors like
tobacco use, diet, associated illnesses, and other exposures,
also in;uence this rate.